Digital (Discrete) input (applicable for IOLAN (S)DS1 D4 or D2R2)
There are two types of Digital input contact types:
Dry contact type: No voltage or current is supplied by the I/O device.
The device senses when a pair of contacts are open or closed

Digital (Discrete) Output (applicable for IOLAN (S)DS1 D4
or D2R2)
Digital output exists when a voltage is applied to a pair of digital output
leads. This voltage can be sourced (sinked) by internal or external sources.
In addition, there can be pulse output when the device is active.

Examples of Digital (Discrete) output devices

Alarms

Control relays

Fans, lights, horns, valves

Motor starters, solenoids

Relay Output ( applicable for IOLAN (S)DS1 D2R2 or A4R2)
Relay output exists when contacts are closed on a pair of relay leads.

Examples of Relay output devices

Alarms

Control relays

Fans, lights, horns, valves

Motor starters, solenoids

Analog Input (applicable for IOLAN (S)DS1 A4 or A4R2)
Analog input exists when variable voltage or current values received from
a sensor corresponds to a floating point decimal value.

Examples of Analog input devices

Temperature sensors

CO2 sensors

Pressure sensors

Humidity sensors

Flow sensors

Potentiometers.

Thermocouple Temperature Sensors (applicable for IOLAN (S)DS T4)
Thermocouple Temperature Sensors are the most popular type of industrial
temperature sensor (widely used in the steel industry and heating applicance
safety). They operate by placing two dissimilar metals together causing
voltage to vary according to the temperature. They are relatively inexpesive
and operate over a wide temperature range.

Types of Thermocouple Temperature Sensors

Type B – 500 to 1800C

Type E – 0 to 1000C

Type J – 0 to 760C

Type K – 0 to 1370C

Type R – 500 to 1750C

Type S – 500 to 1750C

Type T – -100 to 400C

RTD Temperature Sensors (applicable for IOLAN (S)DS T4)
Resistance Temperature Detectors (RTD), also called Resistance thermometers,
are temperature sensors that exploit the predictable change in electrical
resistance of some materials with changing temperature. As they are almost
invariably made of platinum, they are often called platinum resistance
thermometers (PRTs). They are slowly replacing the use of thermocouples
in many industrial applications below 600 °C. Resistance thermometers
are constructed in a number of forms and offer greater stability, accuracy
and repeatability in some cases than thermocouples. While thermocouples
use the Seebeck effect to generate a voltage, resistance thermometers
use electrical resistance and require a small power source to operate.
The resistance ideally varies linearly with temperature.